The Pacific-Antarctic Ridge (PAR, Antarctic Pacific Ridge, South Pacific Rise, South Pacific Ridge) is a divergent tectonic plate boundary located on the seafloor of the South

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five Borders of the oceans, oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is ...

, separating the Pacific plate from the Antarctic plate. It is regarded as the southern section of the

East Pacific Rise The East Pacific Rise (EPR) is a mid-ocean rise (usually termed an oceanic rise and not a mid-ocean ridge due to its higher rate of spreading that results in less elevation increase and more regular terrain), at a divergent tectonic plate bound ...

in some usages, generally south of the Challenger fracture zone which is associated with a triple junction between the Juan Fernández microplate, the Pacific plate and the Antarctic plate. It stretches from there in a general southwesterly direction to the Macquarie Triple Junction south of

New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...

Tectonics

The divergence rate between the two plates along the ridge is believed to vary from about near 65°S to near the Udintsev fracture zone at 55°S. This area of transition in sea floor spreading rate has been mapped by multiple techniques and occurs near the Heirtzler fracture zone. The ridge is related to the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''cre ...

breakup of

Gondwana Gondwana ( ; ) was a large landmass, sometimes referred to as a supercontinent. The remnants of Gondwana make up around two-thirds of today's continental area, including South America, Africa, Antarctica, Australia (continent), Australia, Zea ...

. To the southeast the historic Bellingshausen plate separated the Pacific and Antarctic plates between about 84 to 61 million years ago. Until about 33 million years ago, the Proto-Antipodes fracture zone well to the south separated two independent spreading centers, now merged, being the Antarctic–Pacific Ridge and that of the Antarctic–Campbell Plateau.

Fracture zones

Fracture zone A fracture zone is a linear feature on the ocean floor—often hundreds, even thousands of kilometers long—resulting from the action of offset mid-ocean ridge axis segments. They are a consequence of plate tectonics. Lithospheric plates on eit ...

s are generally areas of low gravity on the seafloor parallel to a spreading center. The named fracture zones going southwest along the rise, include: * Challenger fracture zone * Menard fracture zone * Raitt fracture zone * Heezen fracture zone – northern part of Eltanin fault system which appears continuous to the north with the Louisville Ridge * Tharp fracture zone – southern part of Eltanin fault system * George V fracture zone * Udintsev fracture zone * Le Géographe fracture zone * Astronome fracture zone * Antipodes fracture zone * Le Petit Prince fracture zone * Saint-Exupéry fracture zone * Le Renard fracture zone * La Rose fracture zone * Heirtzler fracture zone ** Endeavour fracture zone (offset from Heirtzler fracture zone poorly defined more recently than about 43.5 Ma – Chron 20) ** Pahemo fracture zone (not defined more recently than about 43.5 Ma – Chron 20) * Pitman fracture zone (initiated as an offset of Kohiku and Pahemo fracture zones around 62.5 Ma – Chron 27) ** Kohiku fracture zone (amalgamates with Pitman more recently than 31 Ma – Chron 12) * Erebus fracture zone * Terror fracture zone * Emerald fracture zone * Hjort fracture zone

The Louisville Ridge

Stretching for north-west from the Eltanin fault system which intersects the Pacific-Antarctic Ridge to the Osbourn Seamount at

Tonga Tonga, officially the Kingdom of Tonga, is an island country in Polynesia, part of Oceania. The country has 171 islands, of which 45 are inhabited. Its total surface area is about , scattered over in the southern Pacific Ocean. accordin ...

and Kermadec Junction is a long line of seamounts called the Louisville Ridge – the longest such chain in the Pacific – thought to have formed from the Pacific Plate sliding over a long-lived center of upwelling

magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma (sometimes colloquially but incorrectly referred to as ''lava'') is found beneath the surface of the Earth, and evidence of magmatism has also ...

called the Louisville hotspot.

Tectonics

Fracture zones

The Louisville Ridge

See also

References

Further reading